Method and apparatus for processing three-dimensional structure, method for producing three-dimensional shape product and three-dimensional structure

ABSTRACT

Disclosed is a method for processing a three-dimensional structure having a fine three-dimensional shape and a smooth surface is disclosed in which the three-dimensional structure is usable for an optical device. 
     The process method comprises the steps of depositing a thin layer for absorption of laser light on a flat substrate; depositing a transparent layer on the thin layer for absorption of laser light; and irradiating a process laser light, passing through the transparent layer; in which pulse injection energy of the process laser light is set to be the same as or smaller than the maximum pulse injection energy capable of exposing a surface of the thin layer in front in the incident direction of the process laser light, and to be set the same as or greater than the minimum pulse injection energy capable of removing the transparent layer in rear in the incident direction of the process laser light.

This application is a divisional of U.S. patent application Ser. No.10/321,635, filed on Dec. 18, 2002, now U.S. Pat. No. 6,803,540.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and an apparatus forprocessing a three-dimensional structure, a method for producing aproduct having a three-dimensional shape, and a three-dimensionalstructure, wherein a fine structure can be formed directly on a materialto be processed by irradiating a laser beam, and more specifically to amethod and an apparatus for processing a three-dimensional structure, amethod for producing a product having a three-dimensional shape, and athree-dimensional structure, wherein a three-dimensional structure witha smooth flat bottom surface can be formed in a high controllabilitywith respect to the process, using one-shot laser light pulses.

In particular, the object of the present invention is to produce in ahigh precision a product which requires to form a very fine structure,and thereby the present invention relates to a product having a finethree-dimensional shape, in which case, a method for forming recordingpits in an optical disk, a method for forming a stamper for producing anoriginal or master form for such an optical disk, a method for formingan optical element, such as a multi-level diffraction grating, adiffraction hologram, or the like, a method for forming an original ormaster form of such an optical element, and/or a method for processing athree-dimensional structure in a micro-machine, micro-sensor or thelike, for processing a micro-structure is applied.

2. Description of the Related Art

Conventionally, the photolithography, together with the etching process,is exclusively employed to process a fine three-dimensional shapeproduct with a high precision. In this case, a desired pattern is formedon a resist material by selectively irradiating light thereto andsubsequently by applying a solution process to the resist material, andthen a material to be processed is etched after the resist material thusprocessed is applied thereto, so that the etching is selectively carriedout for only the surface onto which no resist material is covered. Thatis, the two areas, a part to be processed and another part not to beprocessed, are formed a series of processes, i.e., the application ofthe resist material, exposure, fixation, development, etching of thematerial to be processed and removing the resist material. In the caseof processing a three-dimensional shape product, furthermore, a resistmaterial is newly applied to the material to be processed, and then theabove process is repeated after precisely adjusting the position of thematerial to be processed.

The etching method in the conventional photolithography requires anumber of complicated processes, such as resist application, exposure,development, baking and so on. In the exposure process, the intensity(and time) of the exposure light has to be controlled in a precise anduniform manner in order to avoid a change in the resist pattern due tothe variation of the exposure intensity.

In the case of a three-dimensional process where the depth is altered inaccordance with the position, the shape has to be controlled using anumber of expensive masks.

Moreover, in the case of controlling the depth for each position, anadjustment of precisely positioning the formed substrate is alwaysrequired. Furthermore, the exposure condition is altered for a partiallyprocessed material to be processed, compared with that for a flatsubstrate.

Moreover, it is very difficult to uniformly apply a resist to asubstrate due to the surface roughness, when it is partially processedin a three dimension.

As another example for a method of processing a three-dimensional shapein a fine element, a method using the laser process is known. In theprocess of metals using the conventional laser process method, a highpower laser on the basis of the fundamental wave of CO₂ or Nd: YAG laseris employed.

In recent years, the second or third harmonic of the YAG (YttriumAluminum Garnet), YLF (Yttrium lithium Fluoride) or YVO₄ (YttriumOrthovanadate) is employed in order to realize a fine structure and aprecise process.

As a laser light source used for fine process, an UV pulse laser,typically the excimer laser, is employed.

Such a laser normally has a wavelength of 157 nm to 309 nm and a pulsewidth of several ns to several tens ns. In particular, a polymerabsorbent of light having such a wavelength may be processed to removeportions irradiated by such a laser using a pulse having a smallerwidth, compared with the thermal diffusion length. Therefore, thismethod is known as a process method providing a high precision withoutthermal damage.

In recent years, it is known that the femto-second laser is employed fora method of precisely processing a metal or the like. ID this case, alaser having a pulse width of several tens femto-seconds to severalhundred femto-seconds is used and Ti: sapphire is typically employed forits light source. It is known that this method is capable of providing afine and precise process for various materials made of metal, ceramic orothers. For instance, see the following papers by the present inventors,Kumagawa and Midorikawa: Appl. Phys. A 63, 109–115 (1996); Oyo-buturi(Jpn. J. Appl. Phys.) 67(9), 1051 (1998); and O Plus E 21 (9), 1130(1999).

However, there are difficulties and drawbacks in the above-mentionedconventional laser process methods. For instance, the process using theCO₂ or YAG laser is fundamentally based on the thermal process, so thatit is difficult to process a polymer, low melting material or the likein a high precision, because the material to be processed in thevicinity of the area irradiated by the laser light is thermally deformedand/or melted. In the case of processing metals, thermally disturbedlayers in the vicinity of the process area appear due to a high thermalconductivity, so that the deterioration of shape or profile in the areaoften occurs due to the melting, re-solidification and the like. Inthese cases, such thermal deterioration provides a reduction in thesurface precision for the bottom surface of the processed material to beprocessed and melt marks on the surface.

Moreover, the application of the process using the excimer laser or theharmonic of the YAG laser is generally restricted to the materialshaving high absorption efficiency for such a laser wavelength due to thedifficulty in the process. Actually, such a material pertains to arestricted type of polymers. In this laser process, it is also difficultto form the bottom surface of the material to be processed in a uniformheight and flatness, and it is usually necessary to precisely controlthe beam shape of the laser light using an expensive optical system. Inthis case, it is necessary to process the material to be processed byprojecting in the reduced mode the laser b am whose intensity isuniformed at the mask position by means of an optical element.Nevertheless, it is difficult to provide a three-dimensional process ofthe material to be processed having a uniform bottom surface due to theinterference with the beams diffracted or split from the mask. It isparticularly difficult to form a flat bottom surface in the precision ofthe order of several tens nm, which precision is required for producingoptical elements.

It is known that a high precision can also be obtained even for amaterial to be processed of metal material with the aid of the abrasionprocess using the Ti: sapphire laser having a pulse width in a range ofsub pico-seconds to pico-seconds. In this case, an expensive optics forforming a flat bottom surface must be provided, as similarly saidabrasion is applied. In these lasers, the beam transverse mode isnormally a single mode, and the beams diffracted in the mask are apt tointerfere with each other. Moreover, there arise problems that theflatness of the processed surface is reduced due to speckle pattern anda fine period generates due to the polarization of the laser light,thereby making it difficult to produce flat surfaces in the material tobe processed.

As for the process of a thin layer using a conventional laser, a metalremoving method for correcting a photo-mask is known. In the metalremoving method, a thin metal layer deposited onto a glass substrate isirradiated by a laser light to selectively remove parts of the layer bymelt and evaporation.

In order to produce a three-dimensional structure, a method forlaminating the layers of laser absorbing material is proposed inJapanese Patent Laid-Open Publication No. 10-223504. The other methodsusing a transparent material are proposed in Japanese Patent Laid-OpenPublications No. 10-137953 and No. 10-319221. The former provides amethod for removing a transparent thin layer of an electro-luminescence,in which case, an upper transparent layer is removed using the removingenergy duo to the laser abrasion. The latter relates to a method forproducing a reflection type optical element, in which case, ananti-reflection film is removed by using the abrasion resulting fromlaser light passed through it.

Although the upper thin layer of the material to be processed can alsobe removed by the thin layer processing method using the conventionallaser abrasion, no marked improvement in the surface roughness on thebottom surface of the material to be processed can be obtained, comparedwith that of the above-mentioned laser abrasion. In the case of onlyabsorbent material being employed, a deep depth process can hardly becarried out by a one-shot laser radiation. In case of carrying out adeeper depth process, there is a problem that the quality of thefinished material to be processed may be reduced due to the thermaleffect. In the method of removing the upper layer using the absorbentlayer of the bottom surface, the process of the absorbent layer alsoadvances, so that it is difficult to control the depth in athree-dimensional manner or it is necessary to control the depth byseveral times irradiating the laser light. In any case, it is difficultto control the process of the three-dimensional shape available in anoptical device in the precision of order of nano-meter.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to a method and anapparatus for processing a three-dimensional structure, a method forproducing a three-dimensional shape product and a three-dimensionalstructure, wherein the three-dimensional structure is availableparticularly for an optical device and has a smooth and flat surface,after solving the above-mentioned problems in the conventional laserprocess.

To attain the above object, in a first aspect of the present invention,a method for processing a three-dimensional structure is provided,wherein said method comprising the following steps of: depositing a thinlayer for absorption of laser light on a flat substrate; depositing atransparent layer on the thin layer for absorption of laser light; andirradiating a process laser light, passing through the transparentlayer; whereby the pulse injection energy of the process laser light isset to be the same as or smaller than the maximum pulse injection energywhere the process laser light passes through the transparent layer andis absorbed in the thin layer for absorption of laser light to expose aflat surface as an interface in the thin layer for absorption of laserlight, and to be set the same as or greater than the minimum pulseinjection energy where the process laser light removes the transparentlayer.

In a second aspect of the present invention regarding the method forprocessing a three-dimensional structure according to the first aspect,the thin layer for absorption of laser light has a greater thermaldiffusion rate than the flat substrate.

In a third aspect of the present invention regarding the method forprocessing a three-dimensional structure according to the first orsecond aspect, a portion of the transparent layer, the process laserlight passing through the portion, and a portion of the thin layer forabsorption of laser light, the process laser light penetrating into theportion, are both removed by one-shot pulse radiation of the processlaser light.

In a fourth aspect of the present invention regarding the method forprocessing a three-dimensional structure according to the first or thirdaspect, a thermal insulation layer having a smaller thermal diffusionrate than the flat substrate is deposited on the flat substrate, andthen the thin layer for absorption of laser light is deposited onto thethermal insulation layer.

In a fifth aspect of the present invention regarding the method forprocessing a three-dimensional structure according to the third aspect,the thin layer for absorption of laser light and the transparent layerare further alternately laminated as a plurality of pairs, and aone-shot laser pulse of the process laser light removes a pair of thethin layer for absorption of laser light and the transparent layer,whereby a removed material section having different depths is formed byremoving pairs of the layers in accordance with the number of theone-shot laser pulses.

In a sixth aspect of the present invention regarding the method forprocessing a three-dimensional structure according to one of the firstto fifth aspects, the process laser light is a fundamental or a harmonicof light emitted from an excimer laser or a solid laser and has a pulsewidth of less than 100 ns.

In a seventh aspect of the present invention regarding the method forprocessing a three-dimensional structure according to the third aspect,the thickness of the transparent layers is different from each other.

In an eighth aspect of the present invention regarding the method forprocessing a three-dimensional structure according to the first orsecond aspect, the radiation of the process laser light is carried outby transferring a mask pattern thereto.

In a ninth aspect of the present invention regarding the method forprocessing a three-dimensional structure according to one of the firstto eighth aspects, the process is carried out by shifting the positionof a laminate comprising the flat substrate, the thin layer forabsorption of laser light and the transparent layer relative to theradiation position of the process laser light.

In a tenth aspect of the present invention regarding the method forprocessing a three-dimensional structure according to the third aspect,the process laser light is focused in the form of a round shape toimpinge on the thin layer for absorption of laser light.

In an eleventh aspect of the present invention regarding the method forprocessing a three-dimensional structure according to the third aspect,the process laser light is focused in the form of a straight line toimpinge on the thin layer for absorption of laser light.

In a twelfth aspect of the present invention, the method for producing athree-dimensional shape product is provided, wherein a duplicate isformed from a three-dimensional structure produced by the method forprocessing a three-dimensional structure according to one of the firstto eleventh aspects, and then a three-dimensional shape product havingthe same shape as the duplicate or an inversed shape with respect to theduplicate is formed.

In a thirteenth aspect of the present invention regarding the method forproducing a three-dimensional shape product, the duplicate according tothe twelfth aspect is used as a stamper for a light-recording medium.

In a fourteenth aspect of the present invention regarding the method forproducing a three-dimensional shape product, the duplicate according tothe twelfth aspect is used as a metal mold for a diffraction opticalelement.

In a fifteenth aspect of the present invention, an apparatus forprocessing a three-dimensional structure is provided, the apparatuscomprising: process laser light generating means for introducing aprocess laser light into a thin layer for absorption of laser light,passing through a transparent layer, where a laminate is formed bydepositing the thin layer for absorption of laser light on a flatsubstrate and then by depositing the transparent layer on the thin layerfor absorption of laser light; and process laser light adjusting meansfor adjusting the pulse injection energy of the process laser light,which is introduced from the process laser light generating means viathe transparent layer into the thin layer for absorption of laser light,in which case the pulse injection energy of the process laser light isset to be the same or smaller than the maximum pulse injection energywhere the process laser light passes through the transparent layer andis absorbed in the thin layer for absorption of laser light to expose aflat surface as an interface, and to be set the same or greater than theminimum pulse injection energy where the process laser light removes thetransparent layer.

In a sixteenth aspect of the present invention, an apparatus forprocessing a three-dimensional structure is provided, the apparatuscomprising: process laser light generating means for introducing aprocess laser light into a thin layer for absorption of laser light,passing through a transparent layer, where a laminate is formed bydepositing the thin layer for absorption of laser light on a flatsubstrate and then by depositing the transparent layer on the thin layerfor absorption of laser light; mask means interposed between the processlaser light generating means and the transparent layer; transfer meansfor transferring a pattern in the mask means onto a material to beprocessed; and process laser light adjusting means for adjusting thepulse injection energy of the process laser light, which is introducedfrom the process laser light generating means via the transparent layerinto the thin layer for absorption of laser light, in which case thepulse injection energy of the process laser light is set to be the sameor smaller than the maximum pulse injection energy where the processlaser light passes through the transparent layer and is absorbed in thethin layer for absorption of laser light to expose a flat surface as aninterface, and to be set the same or greater than the minimum pulseinjection energy where the process laser light removes the transparentlayer.

In a seventeenth aspect of the present invention regarding the apparatusfor processing a three-dimensional structure according to the sixteenthaspect, said apparatus further comprising: adjusting means for processposition for adjusting the position of the laminate relative to theprocess position of the process laser light; and laser light controlmeans for controlling the laser light in synchronization with theposition of the laminate.

In an eighteenth aspect of the present invention regarding the apparatusfor processing a three-dimensional structure according to the sixteenthaspect, the mask means allows the transmission pattern of the processlaser light to be varied, and the process laser light can be irradiatedseveral times onto the same portion after changing the transmissionpattern.

In a nineteenth aspect of the present invention regarding the apparatusfor processing a three-dimensional structure according to one of thesixteenth to eighteenth aspects, the process laser light is afundamental or a harmonic of light emitted from an excimer laser or asolid laser and has a pulse width of less than 100 ns.

In a twentieth aspect of the present invention regarding the apparatusfor processing a three-dimensional structure according to the fifteenthor sixteenth aspect, a plurality of pairs of the thin layer forabsorption of laser light and the transparent layer is laminated, and aone-shot laser pulse removes a pair of the thin layer for absorption oflaser light and the transparent layer, whereby a removed materialsection having different depths is formed by removing pairs of thelayers in accordance with the number of the one-shot laser pulses.

In a twenty-first aspect of the present invention, a three-dimensionalstructure including a laminated material to be processed is provided,said three-dimensional structure comprising a flat substrate; atransparent layer capable of transmitting a process laser light towardsthe flat substrate; and a thin layer for absorption of laser lightinterposed between the flat substrate and the transparent layer toabsorb the energy of the process laser light, said three-dimensionalstructure comprising: a removed material section formed by removing bothpart of the transparent layer and part of the thin layer for absorptionof laser light, when the process laser light incident from the side ofthe transparent layer is absorbed in the thin layer for absorption oflaser light; and a bottom surface of the removed material section wherethe thin layer for absorption of laser light remains un-removed at aninterface and exposed in the laser light incident direction.

In a twenty-second aspect of the present invention regarding thethree-dimensional structure according to the twenty-first aspect, thethin layer for absorption of laser light has a larger thermal diffusionrate at a depth of the laser light being incident just thereon than at alarger depth.

In a twenty-third aspect of the present invention regarding thethree-dimensional structure according to twenty-first aspect, the thinlayer for absorption of laser light is made of a material having alarger thermal diffusion rate than that of the flat substrate.

In a twenty-fourth aspect of the present invention regarding thethree-dimensional structure according to the twenty-first aspect, athermal insulation layer is interposed between the thin layer forabsorption of laser light and the flat substrate, and has a smallerthermal diffusion rate than that of the flat substrate.

In a twenty-fifth aspect of the present invention regarding thethree-dimensional structure according to one of the twenty-first totwenty-third aspects, the thin layer for absorption of laser light andthe transparent layer are further alternately laminated, and the removedmaterial section has different depths.

In a twenty-sixth aspect of the present invention regarding thethree-dimensional structure according to the twenty-fifth aspect, thethickness of the transparent layers is different from each other.

In a twenty-seventh aspect of the present invention regarding thethree-dimensional structure according to one of the twenty-first totwenty-sixth aspects, the thin layer for absorption of laser light is ametal layer.

In a twenty-eighth aspect of the present invention regarding thethree-dimensional structure according to one of the twenty-first totwenty-seventh aspects, the transparent layer is a thin layer made ofpolymer.

In a twenty-ninth aspect of the present invention regarding thethree-dimensional structure according to one of the twenty-first totwenty-seventh aspects, the transparent layer is made of ceramicmaterial having a smaller thermal diffusion rate than the thin layer forabsorption of laser light.

In a thirtieth aspect of the present invention regarding athree-dimensional structure according to one of the twenty-first totwenty-ninth aspects, the laminate is processed by transferring a maskpattern thereto.

In a thirty-first aspect of the present invention regarding athree-dimensional structure, a reflection surface is formed on a surfaceof the three-dimensional structure according to one of the twenty-firstto thirtieth aspects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a first embodiment in a method forproducing a three-dimensional structure according to the invention;

FIG. 2 is a sectional view of a second embodiment in a method forproducing a three-dimensional structure according to the invention;

FIG. 3 is a sectional view of a third embodiment in a method forproducing a three-dimensional structure according to the invention;

FIG. 4 is a sectional view of a fourth embodiment in a method forproducing a three-dimensional structure according to the invention;

FIG. 5 is a diagram showing the relationship between the lightpenetrating depth and the wavelength in a fifth or thirteenth embodimentaccording to the invention;

FIG. 6 is a block diagram of an apparatus for processing athree-dimensional structure in an eighth embodiment according to theinvention;

FIG. 7 is a flow chart of controlling the apparatus for processing athree-dimensional structure in the eighth embodiment according to theinvention;

FIG. 8 is a sectional view of the eighth embodiment in a method forproducing a three-dimensional structure according to the invention;

FIG. 9 is a block diagram of an apparatus for processing athree-dimensional structure in a ninth embodiment according to theinvention;

FIG. 10 is a flow chart of controlling the apparatus for processing athree-dimensional structure in the ninth embodiment according to theinvention;

FIG. 11 is a drawing showing the ninth embodiment in a method forproducing a three-dimensional structure according to the invention;

FIG. 12 is a drawing showing a tenth embodiment in a method forproducing a three-dimensional structure according to the invention;

FIG. 13 is a drawing showing an eleventh embodiment in a method forproducing a three-dimensional structure according to the invention;

FIG. 14 is a diagram showing the reflectivity of typical metals in arange of ultra violet to near-infrared wavelength;

FIG. 15 is a sectional view of a fourteenth embodiment in a method forproducing a three-dimensional structure according to the invention;

FIG. 16 is a perspective view of a stamper disk for an optical disk asan example of a three-dimensional structure in a fifteenth embodimentaccording to the invention;

FIG. 17 is a block diagram of an apparatus for processing athree-dimensional structure in a seventeenth embodiment according to theinvention;

FIG. 18 is a detailed block diagram of the apparatus for processing athree-dimensional structure in the seventeenth embodiment according tothe invention; and

FIG. 19 is a flow chart of controlling the apparatus for processing athree-dimensional structure in the seventeenth embodiment according tothe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

FIG. 1 is a sectional view of a first embodiment in a method forproducing a three-dimensional structure according to the invention.

As shown in FIG. 1, the three-dimensional structure 5 comprises a flatsubstrate 1 having a flat and smooth surface of glass, Si, SUS or thelike; a thin layer for absorption of laser light 2 deposited onto theflat substrate 1; and a transparent layer 3 capable of transmitting aprocess laser light 4 towards the thin layer for absorption of laserlight 2. In the case of a SUS substrate being used for the flatsubstrate 1, Al, Cu, Ni or the like may be used as a material for thethin layer for absorption of laser light.

The three-dimensional structure 5 is provided with a removed materialsection having a very small size where part of the transparent layer 3and part of the thin layer for absorption of laser light 2 are removedby the absorption of the process laser light 4 incident from thetransparent layer 3 in the thin layer for absorption of laser light 2;and an interface laminated on the thin layer for absorption of laserlight 2 on the downstream side in the laser light incident direction,i.e., the bottom surface of the removed material section whichcorresponds to the flat surface H remaining un-removed in the surface ofthe flat substrate 1.

As shown in FIG. 1, the thin layer for absorption of laser light 2 madeof a material having a high absorbing efficiency for the process laserlight 4 and a high thermal conductivity is d posited onto the flatsubstrate 1 in the first embodiment of the laser processing method, andthen a transparent layer 3 having a high transparency for the processlaser light 4 is deposited onto the thin layer for absorption of laserlight 2. It is preferable that the flat substrate 1 and the transparentlayer 3 is constituted by a material having a thermal conductivitysmaller than that in the thin layer for absorption of laser light 2.

Thereafter, the layer structure thus laminated is exposed by the processlaser light 4 from the side of the transparent layer 3. In this case,the thickness of each of the layers 2 and 3 and the intensity of thelaser light are adjusted in such a way that the process laser light 4passes through the transparent layer 3 and almost all of its energy isabsorbed in the surface of the thin layer for absorption of laser light2.

The energy absorbed diffuses inside the thin layer for absorption oflaser light 2, and this provides an abrupt increase in the temperatureof the thin layer for absorption of laser light 2. As a result, the thinlayer for absorption of laser light 2 is removed from the flat substrate1 at the interface at which the thin layer for absorption of laser light2 is in contact therewith in a weak coupling force, and the transparentlayer 3 is also removed either simultaneously or contentiously togetherwith the thin layer for absorption of laser light 2. The removal of thethin layer for absorption of laser light 2 and the transparent layer 3at an area at which the process laser light 4 is illuminated causes theflat surface H to be exposed from the surface of the flat substrate 1,thereby enabling a three-dimensional structure 5 having a bottom surfacecorresponding to the removed area to be formed.

In the conventional laser heating process, a rise in the temperatureoccurs in isotropic directions from the irradiated area due to thethermal diffusion of the heat resulting from the laser light in thematerial, so that the removal takes place from the area at which thetemperature of the material arrives at the melting temperature or theevaporation temperature, and a thermally deteriorated layer whoseprofile corresponds to the laser beam intensity from the irradiated areato the bottom surface is produced to form a process trace.

In accordance with the first aspect of the invention, the production ofthe thin layer for absorption of laser light 2 in the form of a verythin layer permits providing an energy selectivity for the process laserlight 4 to the thin layer for absorption of laser light 2. When thelaser light absorption layer is relatively thick, thermal diffusioncauses the thermal deterioration and a melt trace to remain either inthe vicinity of the irradiated area or on the bottom surface of theprocess section. However, the thermally deteriorated area can be greatlyreduced by decreasing the thickness of the laser light absorption layer.

In the process of a substrate including only an absorbing layer, theabove-mentioned isotropic thermal diffusion causes to reduce the amountof removal by one shot laser pulse in order to attain a high precisionin the process. In the present invention, however, a transparent layer 3on the thin layer for absorption of laser light 2 makes it possible toincrease the amount of removal by one shot laser pulse.

Moreover, the provision of the transparent layer 3 permits varying theamount of removal by one shot laser pulse by changing the thickness ofthe transparent layer 3.

Since, in this case, the removal takes place at the interface betweenthe flat substrate 1 and the thin layer for absorption of laser light 2,the smoothness of the flat surface H, which corresponds to the bottomsurface of the removed material section, depends on the smoothness ofthe flat substrate 1. As a result, a flat substrate 1 having a verysmooth surface makes it possible to obtain a three-dimensional structure5 having a flat bottom surface processed in a highly precision.

In the conventional laser abrasion process of a polymer, the polymerhaving a low thermal diffusion rate is used for the light absorptionlayer. In this case, however, the laser-processed portion provides aprofile depending on the distribution of the intensity of the incidentlaser beam. When, for instance, a beam having a Gaussian intensitydistribution irradiates the process area, the area exhibits a profilesimilar to the Gaussian distribution of the intensity of beam, therebymaking it difficult to obtain a flat process area.

In the present invention, however, as shown in FIG. 1, the heat diffusesfrom the irradiated area into the layer in a high rate and the removalcan selectively be carried out at the interface between the flatsubstrate 1 and the thin layer for absorption of laser light 2 as athermal diffusion layer, thereby enabling a smooth surface to beobtained independently of the laser intensity distribution.

In accordance with the present invention, areas to be processed cansimultaneously be removed by the one shot laser pulse and thereforeensures the removal at a much higher rate, compared with that in theconventional laser abrasion method.

Since, moreover, the depth of process is determined by the initial layerthickness, a high precision can be realized for controlling the depth ofprocess.

EXAMPLE 1

Referring to FIG. 1, example 1 of the laser processing method in theinvention will be described.

As shown in FIG. 1, a thin layer for absorption of laser light 2 made ofNi or the like is deposited onto a flat substrate 1 made of glass, Si orthe like, in this example, a glass substrate having a flat uppersurface. A transparent layer 3 made of a light transmitting material,such as acrylic resin, ITO (Indium Tin Oxide) or the like is depositedonto the upper surface of the layer 2. A process laser light 4 havingcertain intensity is spatial-selectively irradiated onto the material tobe processed thus laminated from the upper side of the transparent layer3.

The certain intensity of the process laser light 4 implies the intensitywhere almost all of the energy of the laser light is absorbed in thethin layer for absorption of laser light 2. That is, an injection pulseenergy E0 of the process laser light 4 absorbed in the thin layer forabsorption of laser light 2 via the transparent layer 3 is set to be thesame or smaller than the maximum injection pulse energy E1 where theflat surface H corresponding to the interface on the downstream side inthe incident direction of the laser light can be exposed without anydamage of the flat surface H and to be the same or greater than theminimum injection pulse energy E2 where the transparent layer 3 can beremoved on the upstream side in the incident direction of the laserlight, thereby enabling the process laser light 4 to be absorbed in thethin layer for absorption of laser light 2 via the transparent layer 3.In other words, the injection pulse energy E0, the maximum injectionpulse energy E1 and the minimum injection pulse energy E2 have tosatisfy the relation; E2≦E0≦E1.

The radiation of the process laser light 4 having such intensity causesthe energy of the process laser light 4 to be transmitted inside thethin layer for absorption of laser light 2 due to the thermal diffusionin the thin layer for absorption of laser light 2, thereby causing thetemperature of the thin layer for absorption of laser light 2 to beincreased. Then, the exfoliation takes place at the interface betweenthe thin layer for absorption of laser light 2 and the flat substrate 1,so that the thin layer for absorption of laser light 2 evaporates andpeels off together with the removal of the transparent layer 3.

As a result, the thin layer for absorption of laser light 2 and thetransparent layer 3 are removed only at the laser-irradiated area, sothat the flat surface of the flat substrate 1 is exposed and the flatsurface H having a high smoothness can be obtained at the bottom surfaceof the removed area. Thus, a three-dimensional structure 5 can beobtained and thereby a three-dimensional profile process can berealized.

Second Embodiment

FIG. 2 is a sectional view of a second embodiment in a method forproducing a three-dimensional structure according to the invention.

As shown in FIG. 2, a three-dimensional structure 5 comprises a flatsubstrate 1 made of glass, Si, SUS or the like and having a flatsurface; a thermal isolation layer 6 deposited on the flat substrate 1;a thin layer for absorption of laser light 2 deposited on the thermalisolation layer 6; and a transparent layer 3 for transmitting a processlaser light 4 towards the thin layer for absorption of laser light 2.

Moreover, the three-dimensional structure 6 in the second embodiment isequipped with a finely removed material section formed by removing partof the transparent layer 3 and part of the thin layer for absorption oflaser light 2 due to the absorption of the process laser light 4incident from the side of the transparent layer 3 in the thin layer forabsorption of laser light 2; and an interface on the downstream side ofthe thin layer for absorption of laser light 2 in the incident directionof the thin layer for absorption of laser light 2, i.e., a bottomsurface of the removed material section exposed without removal of aflat surface H corresponding to the surface of the thermal isolationlayer 6 in the case of the second embodiment.

As shown in FIG. 2, the thermal isolation layer 6 as a first materiallayer is deposited onto the flat substrate 1 so as to form a smoothsurface in a laser process method according to the second embodiment.The deposition can be realized by applying, spin coating, dipping orevaporating the thermal insulation material. The thin layer forabsorption of laser light 2, which has high absorption efficiency forthe process laser light 4 and high thermal conductivity, is depositedonto the upper surface of the thermal isolation layer. Moreover, thetransparent layer 3 having a high transparency for the process laserlight 4 is deposited on the upper surface of the thin layer forabsorption of laser light 2 with the same method as in the thermalisolation layer 6. In this case, it is preferable that the thermalconductivity of each of the thermal isolation layer 6 and transparentlayer 3 is smaller than that of the thin layer for absorption of laserlight 2.

Thereafter, the process laser light 4 is irradiated to the laminate fromthe side of the transparent layer 3. The thickness of each of layers 2and 3 and the intensity of the laser light are adjusted such that theprocess laser light 4 passes through the transparent layer 3 and most ofits energy is absorbed in the surface of the thin layer for absorptionor laser light 2.

The energy absorbed in the thin layer for absorption of laser light 2propagates in the thin layer for absorption of laser light 2 and thusthe temperature of the thin layer for absorption of laser light 2abruptly rises, so that the material of the thin layer for absorption oflaser light 2 is removed from the interface between the thin layer forabsorption of laser light 2 and the flat substrate 1 weakly coupled toeach other, thereby enabling the transparent layer 3 to be removedtogether with the thin layer for absorption of laser light 2.

In the second embodiment, adding to the effect obtainable from themethod in the first embodiment, the application of the thermal isolationlayer 6 permits expanding the selectable range of materials for the flatsubstrate 1 and thereby materials providing a relatively less smoothnessare available.

Moreover, the employment of heat-resisting material such as ceramicmaterial for the thermal isolation layer 6 permits increasing theintensity of the process laser light 4, while maintaining a highprecision for processing the bottom surface at the irradiated area, sothat the amount of removal by one shot pulse radiation of the processlaser light 4 can be increased.

Moreover, the employment of polymer, such as polyimide, having a smallthermal conductivity for the thermal isolation layer 6 permits inducingan increase in the temperature of the thin layer for absorption of laserlight 2, thereby enabling a high speed process to be realized with a lowenergy.

EXAMPLE 2

Referring to FIG. 2, the laser process method in the second embodimentof the invention will be described.

As shown in FIG. 2, a thermal isolation layer 6 made of a materialhaving a smaller thermal diffusion rate than that of the flat substrate1, for example, polyimide, is applied in the form of a layer onto a flatsubstrate 1 made of glass, Si or the like and having a flat uppersurface, the flat substrate 1 being made of glass in this example, andthen a thin layer for absorption of laser light 2 made of Al, Cu, Ni orthe like is deposited onto the flat upper surface of the thermalisolation layer 6. In this example, a thin Ni film is employed as thethin layer for absorption of laser light 2. Furthermore, a transparentlayer 3 made of a light-transmitting material, such as acrylic resin,ITO or the like is deposited on the upper surface of the thin layer forabsorption of laser light 2.

A process laser light 4 such as a femto-second titanium sapphire laserlight (femto-second Ti: Sapphire laser light) having a preset intensityis spatial-selectively irradiated to the laminate from the upper side ofthe transparent layer 3. Most energy of the process laser light 4 isabsorbed in the thin layer for absorption of laser light 2 andpropagates inside the thin layer for absorption of laser light 2 afterthe radiation or during the radiation, so that the temperature of thethin layer for absorption of laser light 2 rises. In this case, thethermal diffusion is limited by the thermal isolation layer 6. As aresult, the thin layer for absorption of laser light 2 is removed fromthe thermal isolation layer 6, and the transparent layer 3 is removedtogether with the evaporation and exfoliation of the thin layer forabsorption of laser light 2.

As a result, the thin layer for absorption of laser light 2 and thetransparent layer 3 are removed only at the laser-irradiated area, sothat the flat surface of the thermal isolation layer 6 is exposed andthe flat surface H having a high smoothness can be obtained at thebottom surface of the removed area. Thus, a three-dimensional structure5 can be obtained and thereby a three-dimensional profile process can berealized.

Third Embodiment

As shown in FIG. 3, a three-dimensional structure 7 comprises a flatsubstrate 1 made of glass, Si, SUS or the like having a flat surface; afirst thin layer for absorption of laser light 2 a deposited onto theflat substrate 1; a first transparent layer 3 a deposited onto the firstthin layer for absorption of laser light 2 a to transmit a process laserlight 4 towards the first thin layer for absorption of laser light 2 a;a second thin layer for absorption of laser light 2 b deposited onto thefirst transparent layer 3 a; a second transparent layer 3 b depositedonto the second thin layer for absorption of laser light 2 b to transmitthe process laser light 4 towards the second thin layer for absorptionof laser light 2 b; a third thin layer for absorption of laser light 2 cdeposited onto the second transparent layer 3 b; and a third transparentlayer 3 c deposited onto the third thin layer for absorption of laserlight 2 c to transmit the transparent layer 4.

Moreover, the three-dimensional structure 7 is equipped with a finelyremoved material section (removal area on the left side in FIG. 3) whichis formed by removing part of the third thin layer for absorption oflaser light 2 c and part of the third transparent layer 3 c due to theabsorption of a first time process laser light 4 a incident from theside of the third transparent layer 3 c in the third thin layer forabsorption of laser light 2 c; and an interface for the third thin layerfor absorption of laser light 2 c on the front side in the laser lightincident direction, i.e., a bottom surface (bottom surface on the leftside in FIG. 3) of the removed material section remaining un-removed ona flat surface H corresponding to the surface of the second transparentlayer 3 b in this embodiment.

Moreover, the three-dimensional structure 7 is equipped with a finelyremoved material section (removal area at the center in FIG. 3) which isformed by removing part of the second thin layer for absorption of laserlight 2 b and part of the second transparent layer 3 b due to theabsorption of a second time process laser light 4 b incident from theside of the second transparent layer 3 b in the second thin layer forabsorption of laser light 2 b; and an interface for the second thinlayer for absorption of laser light 2 b on the front side in the laserlight incident direction, i.e., a bottom surface (bottom surface at thecenter in FIG. 3) of the removed material section remaining un-removedon a flat surface H corresponding to the surface of the firsttransparent layer 3 a in this embodiment.

Moreover, the three-dimensional structure 7 is equipped with a finelyremoved material section (removal area on the right side in FIG. 8)which is formed by removing part of the first thin layer for absorptionof laser light 2 a and part of the first transparent layer 3 a due tothe absorption of a third time process laser light 4 c incident from theside of the first transparent layer 3 a in the first thin layer forabsorption of laser light 2 a; and an interface for the first thin layerfor absorption of laser light 2 a on the front side in the laser lightincident direction, i.e., a bottom surface (bottom surface on the rightside in FIG. 3) of the removed material section remaining un-removed ona flat surface H corresponding to the surface of the flat substrate 1 inthis embodiment.

As shown in FIG. 3, in the laser process method of the third embodiment,the first thin layer for absorption of laser light 2 a having a highabsorption rate for the process laser light and a high thermalconductivity is deposited in the form of a thin film on the flatsubstrate 1. Thereafter, the first transparent layer 3 a having a hightransparency for the process laser light is deposited onto the firstthin layer for absorption of laser light 2 a. Furthermore, the secondthin layer for absorption of laser light 2 b and the second transparentlayer 3 b are alternately laminated at least two times on the uppersurface of the first transparent layer 3 a. In this case, it ispreferable that the materials of the flat substrate 1 and thetransparent layers 3 a–3 c have a smaller thermal conductivity than thatof the thin layer for absorption of laser light 2.

Thereafter, the process laser light 4 a is irradiated to the laminatefrom the side of the third transparent layer 3 c, at three differentpositions in this embodiment. The thickness of the two uppermost layersand the intensity of the process laser light are adjusted such that theprocess laser light 4 a passes through the third transparent layer 3 cand most of its energy is absorbed in the surface of the third thinlayer for absorption of laser light 2 c.

The absorbed energy of the process laser light 4 a is propagated in thethird thin layer for absorption of laser light 2 c, and therefore thetemperature of the third thin layer for absorption of laser light 2 cabruptly rises. This causes inducing the removal of material from theinterface between the third thin layer for absorption of laser light 2 cand the second transparent layer 3 b weakly coupled with each other,thereby enabling the second transparent layer 3 b to be removedsimultaneously or sequentially together with the third thin layer forabsorption of laser light 2 c.

In this embodiment, one-shot pulse of the process laser light 4 b isagain irradiated to the same center and right hand areas to remove thesecond thin layer for absorption of laser light 2 b and the secondtransparent layer 3 b. Such a selective radiation of the process laserlight ensures a digital control of the depth for processing areas,thereby enabling a fine three-dimensional structure having a flat andsmooth bottom surface H to be produced.

In the above description, the process laser light is irradiatedsequentially at three portions, two portions and a portion to form thethree-dimensional structure 7. However, the three-dimensional structure7 can also be produced by sequentially irradiating a portion where thematerial should be removed at the greatest depth; two portions, i.e.,the above-mentioned portion and a second portion where the materialshould be removed at a next greater depth; and three portions, i.e., thefirst portion, second portion and a third portion where the materialshould be removed at a next greater depth. The order of the irradiatedportions can be altered arbitrarily. The above description is providedfor three removed areas. However, the selective radiation can also becarried out for more than three portions.

As described above, the third embodiment indicates that the number ofthe laser radiation can digitally control the depth of processing.

This also indicated that the re-adjustment or alignment of positionscarried out after removing the substrate in the process ofphotolithography is no longer required, and a desired three-dimensionalshape can be spatial-selectively produced only by means for eithercontrolling the position of the laser process or moving the substrate.

The process method of the third embodiment makes it possible tomanufacture, for instance, a multi-binary diffraction optical element, ahologram optical element based on the computer-controlled position ofprocess, or the like.

EXAMPLE 3

As shown in FIG. 3, a thin layer for absorption of laser light 2 a madeof Ni is deposited on a flat substrate 1 made of glass at a thicknessof, for instance, 50 nm by sputtering, and then a transparent layer 3 aof ITO is deposited on the upper surface of the thin layer forabsorption of laser light at a thickness of, for instance, 100 nm bysputtering. Moreover, Ni is similarly deposited to the upper surface ofthe transparent layer 3 a by sputtering to form a thin layer forabsorption of laser light 2 b and further ITO is deposited at the samethickness to form a transparent layer 3 b. By repeating the processed, alaminate of a multi-layer structure can be produced.

A process laser light, such as a femto second Ti: sapphire laser lightor the like having an intensity, is spatial-selectively irradiated tothe laminate from the upper side of the transparent layer 3 c. Theenergy of the process laser light 4 a is mostly absorbed in the thinlayer for absorption of laser light 2 c and after or during the laserradiation the energy is propagated in the thin layer for absorption oflaser light 2 c, thereby causing the temperature of the thin layer forabsorption of laser light 2 c to be increased. Hence, the uppermost ITOlayer and the Ni layer disposed beneath thereof are removed by one-shotlaser pulse. Thereafter, the radiation position is shifted and the laserlight is irradiated to the middle ITO layer and the Ni layer disposedbeneath thereof. In this case, the layer is removed in accordance withthe number of pulses, and a three-dimensional shape having atwice-greater depth than in the initial removed area is produced. Byfurther shifting the irradiating position and by changing the number ofpulses, a three-dimensional structure 7 having a varied thickness can beobtained.

Fourth Embodiment

FIG. 4 is a sectional view of a fourth embodiment in a method forproducing a three-dimensional structure according to the invention.

As shown in FIG. 4, the three-dimensional structure 9 has the same layerarrangement as that of the third embodiment shown in FIG. 3, except fora difference in the thickness of the respective layers. The method forprocessing the three-dimensional structure in the fourth embodiment isthe same as that in the third embodiment.

A substantial difference from the third embodiment is that the thicknesscan be altered for one of the thin layer for absorption of laser light sand one of the transparent layers, respectively. As for, e.g., awavelength λ of a reference laser light used for an optical element, thethickness is set to be λ/2 for the first layer and λ/4 for the secondlayer. In this case, it is desirable that the thermal conductivity forthe flat substrate 1 and the transparent layer 3 a, 3 b, 8 is smallerthan that for the thin layer for absorption of laser light s.

Thereafter, a process laser light 4 a is irradiated to the laminate fromthe side of the transparent layer 8. The thickness of two outer layersand the intensity of the laser light is adjusted such that the processlaser light 4 a passes through the transparent layer 8 and its energy ismostly absorbed in the surface of the thin layer for absorption of laserlight 2 c.

The energy absorbed is propagated in the thin layer for absorption oflaser light 2 c, and therefore the temperature of the thin layer forabsorption of laser light 2 c abruptly rises, so that the thin layer forabsorption of laser light 2 c is removed from the interface between thethin layer for absorption of laser light 2 c and the transparent layer 3b weekly coupled with each other on the lower surface side of the thinlayer for absorption of laser light 2 c, thereby enabling thetransparent layer 8 to be removed simultaneously or continuouslytogether with the thin layer for absorption of laser light 2 c.

Furthermore, one-shot pulse of the laser light is irradiated to the sameportion provides a removal of the transparent layer 3 b and the thinlayer for absorption of laser light 2 b adjacent to the lower surfaceside of the removed thin layer for absorption of laser light 2 c.

Such a selective radiation of the process laser light causes the depthof process area to be digitally controlled, so that a finethree-dimensional structure having a smooth bottom surface can beproduced.

In the fourth embodiment, the thickness control of the transparent layerin the initial stage can expand the controllable range of the depth inthe processed area without any alteration of the radiation intensity ofthe process laser light.

Hence, pulses of the laser light irradiating a selected area of theelement having a varied depth can be digitally controlled. Furthermore,for instance, phase modulation elements, whose property is altered withthe change of the depth, can be spatial-selectively formed on asubstrate.

EXAMPLE 4

As shown in FIG. 4, a thin layer for absorption of laser light 2 a of athin Ni layer is deposited onto a flat substrate 1 of glass bysputtering and a first transparent layer 3 a is further deposited ontothe thin layer for absorption of laser light 2 a. In this case, thetotal thickness of the thin layer for absorption of laser light 2 a andthe transparent layer 3 a should be set to be λ/4 for a wavelength λ.Then, a thin layer for absorption of laser light 2 b and a transparentlayer 3 b both having the same thickness are similarly deposited, andfurther a thin layer for absorption of laser light 2 c as a thirdabsorbing layer and a transparent layer 8 are deposited. In this case,the total thickness of the thin layer for absorption of laser light 2 cas the third absorbing layer and the transparent layer 8 as the thirdtransparent layer should be set to be λ/2 by altering the thickness ofonly the transparent layer 8.

By so doing, a multi-layer structure having a thickness different in therespective layers can be produced. Then, a process laser light 4 a, suchas femto second Ti: sapphire laser light, having a preset intensity isspatial-selectively irradiated to the laminate from the side of thetransparent layer 8. The energy of the process laser light 4 a is mostlyabsorbed in the thin layer for absorption of laser light 2 c andpropagated in the thin layer for absorption of laser light 2 c afterradiation or during radiation, so that the temperature of the thin layerfor absorption of laser light 2 c rises. Then, the layers at one portioncan be removed by one-shot pulse radiation. Thereafter, aspatial-selective removal of layers is carried out by controlling thelaser illumination position and the number of laser illumination pulses.Since the thickness of only the transparent layer 8 is altered, athree-dimensional structure 9 having a varied depth can be producedwithout substantial alteration of the radiation energy. Thethree-dimensional structure 9 can spatially alter the phase for areference wavelength λ, and therefore is available for a wave frontcontrolling element. This provides an applicability of producing anelement in which, for instance, a ½-wavelength plate and a ¼-wavelengthplate can be integrated on a single substrate.

Fifth Embodiment

In the laser process method according to one of the first to fourthembodiments, the thin layer for absorption of laser light is a thinmetal film made of a metallic material, such as Ni, Al, Au or the like.In this case, the thin metal film is formed from the above metallicmaterial in a thickness of several nm to several hundred nm by means ofthe evaporation, sputtering, CVD or the like.

The metallic material has a strong absorption in the vicinity of thesurface for radiation having a wavelength in a range of ultraviolet orfrom visible to infrared light. It is known that the light absorbinglength (light penetrating length) D can be expressed by the followingequation (1).D=α ⁻¹=λ/4πκ,  (1)where κ is the complex dielectric constant, α is the absorptioncoefficient and λ is the wavelength.

The light penetrating length for typical metals is shown as a functionof the wavelength in FIG. 5. It can be recognized that for thesemetallic materials the absorption of the light occurs within a veryrestricted range of several tens nm in a wide range. It is also wellknown that the heat transmission rate in the metallic material isextremely high and that the heat transmitting distance (thermaldiffusion length) L can be expressed as a function of the transitionperiod τ by the following equation (2):L=√(dτ)  (2)where d is the thermal diffusion rate.

Since the heat transmission rate is so high and the light is absorbed inthe surface, the metal thin films laminated at a thickness of, forinstance, several tens nm is thermally excited by the light illuminationand tends to become a high temperature at a very high speed. In thiscase, the thin metal layer is sandwiched between other materials so thatthe heat is accumulated therebetween. As a result, only the thin metallayer and the flat substrate are removed after thermally separated fromthe flat surface being in contact with the thin metal layer. Thethickness of the material is of order of several tens nm and thereforethe heat transmission range can be set to be such a magnitude.Accordingly, a high precision process restricted in the vicinity of thelaser illumination area is feasible.

Metal can advantageously be used, since it can easily be deposited orapplied to another material in the form of a thin film, and further thecost of production is very small.

Sixth Embodiment

A laser process method of the sixth embodiment is the same as those ofthe first to fourth embodiments. In this case, a transparent layer ismade of a polymer transparent for the process laser light. In the caseof the process laser light in a range from the visible to the infraredlight, the polymer can be selected from an acrylic resin, a PET resin, apolyimide resin or the like. In the case of the process laser light usedin an ultraviolet range, a polymer containing fluorine, an acrylic resinhaving high transparency, a poly carbonate resin having hightransparency or the like can be used.

The transparent layer can be formed by spin coating or dipping a liquidresin under an appropriate control of the layer thickness.

The usage of polymer for transparent material makes it possible toproduce the transparent layer having a controlled layer thickness withreduced cost. Such a liquid material provides an easy thickness controland permits hardening with heat or light, so that the layer can beprepared in a wide thickness range.

In addition, a wide selectable range for the material makes it easy todetermine with a reduced cost a desired material, which ensures a hightransparency for the process laser light and has a reduced thermaldeterioration.

Seventh Embodiment

A laser process method of the seventh embodiment is the same as those ofthe first to fourth embodiments, and a ceramic material is used for thetransparent layer. ITO, titanium oxide or the like can be used for thetransparent material. In this case, the transparent layer is prepared bysputtering under the thickness control.

The usage of ceramic material for the transparent layer permitsproviding a highly precise process with reduced thermal damage. Avariety of the materials make it possible to easily select a materialhaving a high transparency for the process laser light.

In addition, these materials permit forming a layer in a thickness oforder of nm by sputtering or the like, thereby enabling the depthcontrol to be performed in high precision.

Since the melting point of these materials is much greater than that ofmetals, the energy of the laser beam incident to a metal can beincreased in the case of a multi-layer, thereby allowing a greateramount of removal to be attained with one-shot laser pulse.

Moreover, these materials ensure a reduced thermal deterioration as wellas the processing with a high quality.

Eighth Embodiment

As shown in FIG. 6, a process apparatus of the eighth embodimentcomprises a laser process device 31 for emitting a process laser light32; a mask 38 such as a photo-mask through which part of the processlaser light 32 emitted from the laser process device 31; a mask movementstage 52 for moving the mask 38; a mirror 37 for reflecting the processlaser light 32 passing through the mask 38; a focusing lens 39 forprojecting in a reduced magnification a pattern image resulting from theprocess laser light 32 reflected by the mirror 37; a movement stage 41for movably supporting a laminate 51 as a material to be processed inthe embodiments 1 to 7; and a computer 53 for controlling the laserprocess device 31, the movement stage 41 and the mask movement stage 52.

As shown in FIG. 7, the computer 53 locates the laminate 51 as a processsample in a predetermined position at step S1, and moves the laminate 51in a process position using the movement stage 41 at step S2, and thenmoves the mask 38 in a predetermined position using the mask movementstage 52 at step S3.

Subsequently, a removed material section is formed in the laminate 51,by irradiating the process laser light 32 thereto from the laser processdevice 31 at step S4.

Subsequently, at step S5, it is judged whether or not the laserradiation is completed, and in the non-completed case, returning to stepS2 to move the laminate 51 in another process position by moving themovement stage 41.

At step S6, the process for forming the profile is finished.

As can be seen, the process method of the eighth embodiment is similarto those of the first to fourth embodiments. Using the mask 38 preparedby etching a metal, evaporating chromium or the like, the process laserlight is projected to the laminate in a reduced magnification ordirectly with mask contact to form a process pattern corresponding tothe mask pattern.

In the laser process method of this embodiment, the process laser light4 is spatial-selectively absorbed in the thin layer for absorption oflaser light 2, as shown in FIG. 8(B). The light energy absorption in thethin layer for absorption of laser light 2 and the heat diffusionthereafter allow the laser-irradiated area to be increased intemperature, thereby enabling the thin layer for absorption of laserlight 2 and the transparent layer 3 deposited thereon to be removed atthe area. In this case, various profiles can be produced with theone-shot pulse radiation using an appropriately selected mask.

In the conventional abrasion process using the excimer laser, astructure formed on a photo-mask in an area of several mm square isprojected in a reduced magnification of ⅓ to ⅕ onto the surface of amaterial to be processed to form a desired profile.

In this ease, a non-uniform spatial distribution at the irradiated arearesults from the non-uniform intensity in the laser light and thediffraction effect in the mask edges. To avoid the non-uniformity, anumber of expensive optical elements must be adjusted. In theconventional laser abrasion method, the non-uniform intensitydistribution of the laser provides a three-dimensional profilecorresponding to the intensity distribution of the irradiating laserlight at the irradiated area. In the process method of this embodiment,however, all the areas of the layer where the heat diffuses are removed,thereby enabling a smooth bottom surface to be formed.

Moreover, in the conventional laser abrasion method, it is necessarythat an expensive optics is used to eliminate the change in the beamshape due to the diffraction and interference at the edges of the maskopening in order to enhance the smoothness in the processed areas. Inthe method of this embodiment, however, the spatial-selected removal ofmaterial at all the irradiated areas can be achieved with highly smoothsurfaces, even if there is non-uniform intensity distribution due to thediffraction and/or the interference.

In this case, it is possible to continuously process a wide area bycontrolling the position of the material to be processed with stages.

EXAMPLE 8

FIG. 8 shows a difference between the structure obtained by the methodfor processing a three-dimensional profile by transferring a mask imagethereto in this embodiment (FIG. 8(B)) and the structure obtained by theconventional method for removing the material by abrasion (FIG. 8(A)).

In the case of applying the conventional laser abrasion process to alaminate as a structure consisting of thin layers, a desired part of atransparent layer 3P can be removed by the abrasion effect for theabsorbing layer 2P on a substrate 1P. However, there remain uneven areason the bottom surface 10 a due to the non-uniformity in the laser lightintensity distribution, the thermal property of the absorbing material,the orientation of the polymer and the like, as shown in FIG. 8(A).

On the contrary, the energy of the laser light is rapidly propagated inthe thin layer for absorption of laser light 2, thereby increasing thetemperature of the thin layer for absorption of laser light 2 at theirradiated areas in this embodiment. Accordingly, a rapid separation ofthe thin layer for absorption of laser light 2 from the flat substrate 1takes place at the area, together with the transparent layer 3.

In this case, the thin layer for absorption of laser light 2 isseparated at the whole irradiated areas, so that a smooth process isfeasible since a smooth and flat surface 11 a of the flat substrate 1 isexposed as a bottom surface.

When, for example, the width of process is several micrometers, and thethickness of the thin layer for absorption of laser light 2 is severaltens nanometers, an increase in the width of process due to the heattransmission is negligibly small and therefore a high precision processcan be realized.

Ninth Embodiment

A process apparatus shown in FIG. 9 comprises a laser device 31 foremitting a process laser light 32; a pockels cell 31 a disposed insidethe laser device 31; a mask 38 such as a photo-mask through which partof the process laser light 32 from the laser device 31 passes; amovement stage 52 for moving the mask 38; a mirror 37 for reflecting theprocess laser light 32 passed through the mask 38; a lens 39 forprojecting a mask pattern image at a reduced magnification onto thesurface of a laminate 51 of a material to be processed in theembodiments 1 to 7 by the process laser light 32 reflected from themirror 37; a movement stage 41 for movable supporting the laminate 51;and a computer 53 for controlling the laser device 31, the movementstage 41 and the movement stage 52.

As shown in FIG. 10, the computer 53 locates the laminate 51 as aprocess sample at a predetermined position at step S1, and moves thelaminate 51 to the process position by operating the movement stage 41at step S2, and further moves the mask 38 in a predetermined position byoperating the movement stage 52.

Subsequently, at step S4, the process laser light 32 emitted from thelaser device 31 by controlling the pockels cell 31 a is irradiated ontothe laminate 51 to form the removed material section.

Subsequently, at step S5, it is judged whether or not the laserradiation is ended. In the case of being not ended, returning to stepS2, the laminate 51 is moved in the next process position by operatingthe movement stage 41.

At step S6, the processing of the profile is finished.

The process method of this embodiment is a mask projection type laserprocessing method. The laser irradiating position canspatial-selectively be altered by using the photo-mask 38, which is madeof a transmission type liquid crystal, a reflection type mirror elementor the like. The processing of the profile is carried out by controllingthe laser radiation and the shape of mask openings in a sychronizedmanner.

In the ninth embodiment, the mask of a transmission type liquid crystalhaving, e.g., a high transparency for the process laser light is used bysynchronizing it with the process laser light, and so the mask shape isaltered in accordance with the laser radiation period, switching betweena first period and a second period.

In this case, a reflection type mirror array elements used in aprojector can also be employed as another variable mask, if the elementshave a high reflectivity for the process laser light.

With this structural arrangement, the digital depth control is feasible;for instance, along with the shifting of the laser radiation position,the depth of process can be increased by increasing the number of laserpulse shots.

In this case, the same intensity profile can be used for the processlaser light, so that a high speed process can be attained with a reducedcost, compared with the process method in which a plurality of masks aresequentially changed.

EXAMPLE 9

FIG. 11 shows an embodiment in which a transmission type liquid crystalmask is used.

A process laser light having an intensity distribution 12 shown in FIG.11(A) is irradiated to a transmission type liquid crystal mask 13 a. Thelaser intensity after passing through the mask can spatially be alteredby means of the transmission type liquid crystal mask 13 a and apolarizing beam splitter interposed between the mask and the radiationarea. In this case, the intensity of the transmitted light can bechanged from the maximum to about 0 by controlling the orientation planeof the liquid crystal. In this embodiment, the intensity of the lightpassed through the mask has a binary value, the maximum or minimumvalue. However, more than two values of the intensity can be allowed inorder to obtain an optimum process state. By projecting the transmittedlight onto the surface of the material to be processed 14 a at a reducedmagnification, a three-dimensional pattern is formed using a first laserlight. Thereafter, the mask shape is changed into a second mask shape 13b before the second laser radiation period, as shown in FIG. 11(B), andthen a part of the material to be processed 14 b is removed, using theprocess laser light passed through the second mask shape 13 b. At aposition at which the first laser light and second laser light areirradiated, two layers are removed, whereas at a position at which oneof these is irradiated a single layer is removed. By repeating theseprocedures, a three-dimensional profile of the material to be processed14 c can be obtained, as shown in FIG. 11(C).

The transmission type liquid crystal 13 a permits producing athree-dimensional profile in a high speed and makes it possible toproduce any arbitrary by synchronizing the variation of the transmittedlight intensity with the timing of the laser radiation.

Hence, such a three-dimensional product can be manufactured with areduced cost without usage of many masks.

Tenth Embodiment

A laser process method of the tenth embodiment is the same as those ofthe first to fourth embodiments. In the method, a process laser light isfocused and a round pattern is produced by one-shot pulse of the focusedlight beam. In this case, the light intensity at an irradiated area canbe adjusted by means for varying the intensity of the laser light.

A laminate as a structure of thin layers is disposed on a movement stageand the process position is determined with a high speed by the movementstage.

In this case, it is desirable that the process laser light has aGaussian intensity distribution and that an objective lens disposed soas to have a long distance between the outer lens surface and theprocess position is used to focus the process laser light.

Moreover, it is preferable that a focus adjusting mechanism is includedin movement means in order to avoid the position deviation at the laserprocess position in the laser irradiating direction.

In the process method according to the tenth embodiment, a process laserlight, which has a general Gaussian intensity distribution in a singlemode laser, is focused and irradiated to the surface of a thin layer forabsorption of laser light. In this case, the irradiated position iscontrolled by a linear stage and a rotation stage, and determined bysynchronizing the movement of these stages with the process laser light.The direction of laser radiation relative to the direction toward thethin layer for absorption of laser light is also determined bysynchronizing these stages with the laser radiation.

Hence, the laser light having a Gaussian intensity distribution isfocused and irradiated onto the surface of the thin layer for absorptionof laser light, so that the heat is propagated in the thin layer forabsorption of laser light and the temperature rises in the area of thethin layer for absorption of laser light, thereby causing the thin layerfor absorption of laser light to be separated from the lower surface.Since the thin layer for absorption of laser light and the transparentlayer are removed only at the irradiated area, the profile after theprocess becomes a cylindrical shape and therefore a bore having a smoothbottom surface can be processed.

In this case, the light absorbing area in the layers, the energy oflight and the heat transmitting area in the layers can be adjusted bycontrolling the laser light radiation intensity, thereby enabling thediameter of the bore to be adjusted.

By moving the material to be processed in synchronization with the laserradiation, the bores can be sequentially formed, and a plurality ofthree-dimensional profiles can be produced in a high rate by rapidlyshifting the material to be processed.

EXAMPLE 10

Referring now to FIG. 12, the variation of the processed shape due tothe energy of the focused light will be described.

In the laser process by this embodiment, the removable of the thin layerfor absorption of laser light can be attained by heating the thin layerfor absorption of laser light. In this case, the intensity of theincident laser light has to be set more than a threshold value in orderto locally remove the thin layer for absorption of laser light and thetransparent layer.

Since the light having an intensity of more than the threshold valueprovides a removal of the thin layer for absorption of laser light andthe light having an intensity of less than the threshold value providesno removal, an incident light is formed by focusing the laser beamhaving a light intensity of, e.g., a Gaussian profile, thereby theprocessed area can be controlled by the laser light intensity.

For instance, when a laser having a Gaussian intensity distribution isirradiated onto the surface of a material to be processed, as shown inFIG. 12(A), the laser light having an intensity of more than thethreshold provides a three-dimensional structure 15 a. A decrease in thelaser light intensity using intensity adjusting means, as shown in FIG.12(B), provides a three-dimensional structure 15 b whose size is reducedrelative to the structure 15 a in FIG. 12(A).

A further decrease in the laser light intensity, as shown for theintensity distribution in FIG. 12(C), provides a very finethree-dimensional structure 15 c, which can hardly be obtained with theconventional exposure method.

Eleventh Embodiment

A process method of the eleventh embodiment is the same as those of thefirst to fourth embodiments. In this case, a process laser light isfocused in one direction by a combination of cylindrical lenses togenerate a beam in the form of a straight line, and then the beam isspatial-selectively irradiated onto a thin layer for absorption of laserlight. A laminate as a material to be processed is moved by moving meanssuch as stage or the like in synchronization with the laser beam.

A three-dimensional structure having smooth bottom surfaces can besequentially obtained by repeating the radiation of laser light and themovement of the stage.

In the process method according to the eleventh embodiment, aline-shaped pattern is formed on the surface of the structure byirradiating the process laser light. In this case, the laser beam has aGaussian intensity distribution in the transversal direction and auniform intensity distribution in the longitudinal direction, as shownin FIG. 12(A). The surface of the thin layer for absorption of laserlight is irradiated by a process laser light having such intensity andthen the heat is thermally diffused in the layer, so that thetemperature of the thin layer for absorption of laser light rises andthen the exfoliation takes place in the bottom surface. In this case,the removal takes place in the thin layer for absorption of laser lightand the transparent layer at the irradiated area, so that bores having asmooth bottom surface can be obtained.

Since the exfoliation is carried out over all the area in the thicknessdirection, a profile having a smooth bottom surface can be obtained evenif the laser beam having a Gaussian intensity distribution.

In conjunction with the above, the control of the laser light intensitymakes it possible to control the light absorbing area in the thin layerfor absorption of laser light, the energy and the heat diffusion area ofthe thin layer for absorption of laser light, thereby enabling theprocess width to be controlled.

The movement of the laminate in synchronization with the laser radiationpermits sequentially producing bores, and thus a line shaped profile canbe produced in a high speed.

By applying this method, a grating as a diffraction type optical elementcan easily be produced, and by applying the positional alignment ofmulti-layer, a multi-level diffraction grating can easily be producedonly with a movement of the material to be processed.

EXAMPLE 11

A process laser light beam having an intensity distribution 16, as shownin FIG. 13(A), is formed, using a cylindrical lens or mirror. Aspatial-selective radiation of the process laser light is continuouslycarried out either by scanning the laser beam or by moving the materialto be processed, in which case, the timing of the laser light radiationand the radiation position is controlled in synchronization with eachother by means of movement means to radiate the process laser light ontoa desired position in the form of a line.

With a scanning pitch from several micrometers to several hundredsmicrometers, for example, a multi-binary type diffraction grating 17shown in FIG. 13(B) or a master form thereto can be produced.

Twelfth Embodiment

A process method of the twelfth embodiment is the same as those of thefirst to fourth embodiments. The process laser light is generated eitherby Q switching the fundamental from an excimer laser having a pulsewidth of less than 100 ns or a solid laser such as Nd: YAG, Nd: YLF, orthe like, or by introducing the laser light into, for instance, anon-linear optical medium to produce a harmonic. At present, a highpower laser light source can be selected from the above-mentioned lasersand the thickness of the thin layer for absorption of laser light ispreferably set to be less than the width of the laser-irradiated area.

In particular, light from a laser having a pulse width of less than 100ns is used as the process laser light in order to reduce the thermaldiffusion area.

It is known that the thermal diffusion rate due to the heat propagationin a material is given by equation (1), as described above. From theequation, it follows that the thermal diffusion length at time τ afterirradiated in a material having a thermal diffusion rate d is L.

Pulse laser light having a pulse width of less than 100 ns provides athermal diffusion distance of less than 1 micrometer in the thin layerfor absorption of laser light for normal ceramic, polymer materials andthe like. Accordingly, the usage of the process laser light having apulse width of greater than the above pulse width permits restrictingthe thermal diffusion range, thereby enabling the deformation due to thethermal diffusion to be reduced.

When the thickness of the thin layer for absorption of laser light isless than the thermal diffusion distance L and the area of laserradiation is greater than L, the removal of thin layers only at theirradiated area and the process of a three-dimensional structure can becarried out in a highly precise manner.

When the radiation area of the process laser light is in a range fromsub-micron to several hundred micrometers and the thickness of the layeris of order of sub-micron, a three-dimensional profile having a smoothbottom surface, whose area is substantially the same as the laserradiation area, can be obtained.

EXAMPLE 12

Equation (1) for diffusion represents the range within which energyimpinged at a moment diffuses after a certain time. The thermaldiffusion rates for various materials are listed in Table 1.

TABLE 1 Material Thermal diffusion rate (d) Metal  20–200 × 10⁻⁶ Glass0.3–2 × 10⁻⁶ Polymer 0.2–0.5 × 10⁻⁶where the thermal diffusion rate d at ordinary temperature is shown fortypical metals, glasses and polymers.

The thermal diffusion range obtainable from the pulse width of theprocess laser light is listed for the above materials in the followingTable 2:

TABLE 2 Thermal diffusion range (μm) 1 ps 1 ns 1 μs Metal −0.01 −0.3 −10Glass 0.001 0.03 1 Polymer <0.001 0.02 0.5

As can be seen, a pulse width of less than 100 ns in the process laserlight ensures a thermal diffusion range of <1 μm for these typicalmaterials. Therefore, when the layer thickness is less than the abovevalue, the heat is completely transmitted inside the thin layer forabsorption of laser light in the thickness direction, thereby allowingthe thermal removal to be realized.

Accordingly, a three-dimensional structure having a smooth bottomsurface can be processed in a high precision.

Thirteenth Embodiment

A process method of the thirteenth embodiment is the same as those ofthe first to fourth embodiments. In particular, the fundamental or theharmonic of Ti: sapphire laser having a pulse width of order of sub-picoseconds, or the fundamental or the harmonic of a solid laser such as Nd:YAG laser is employed as a process laser light, and a layer of metal,such as Ni, Au, Al or the like is used as a thin layer for absorption oflaser light. It is desirable that the thickness of the metal layer ismore than, or preferably several times greater than the penetrationrange of the laser light.

In the thirteenth embodiment, a laser having extremely small pulse widthless than 1 ps is used. In accordance with the recent development, sucha laser can be realized typically by Ti: sapphire laser, which has acenter resonant wavelength in the vicinity of 800 nm and a typical pulsewidth of several tens fs to about 200 fs.

It is known that the laser having such extremely small pulse widthprovides a particularly short period of radiation to the material,thereby allowing the thermal deterioration to be suppressed and a highprecision process to be realized. See, for example, the followingarticle: (Appl. Phys. A 63, 109–115 (1996)).

It is also known that the abrasion process is feasible even formaterials, such as metals, having a high thermal conductivity byutilizing the laser having a very small pulse width.

Moreover, it is known that metal has a high absorption coefficient overa wide spectral range from ultraviolet to near infrared light, and thephoto-absorption takes place inside an extremely thin layer of thesurface. For typical metals, the light penetrating range is shown inFIG. 5, and the reflectivity at various wavelengths is further shown inFIG. 14. The energy of light, which is not reflected by a metal, isabsorbed in the vicinity of the metal surface, and immediatelytransformed into heat within the area represented by the penetrationrange shown in FIG. 5.

During a period less than a picosecond, the electron temperature is notsame as the lattice temperature, and these temperatures can be expressedby a two-temperature diffusion equation, as described in theabove-mentioned article.

The energy of laser light is transferred to the lattice system inseveral pico-seconds and then propagated therein as heat, therebycausing the removal to take place in the laser light-irradiated area.

In accordance with the present invention, the metal material isdeposited as a thin layer for absorption of laser light and thereforethe range of thermal diffusion is limited. As a result, the thermaldiffusion in the metal is restricted, thereby enabling the metal layerto be removed from the flat surface with a low light energy.

Normally, metals have an extremely large diffusion range, and thereforethe width or distance of the removed area from the laser-irradiatedposition is expanded However, using light having a pulse width of orderor sub-pico second, the diffusion width can be maintained within lessthan 1 micrometer for typical metals.

Light emitted from the Ti: sapphire laser is near infrared light and itis applicable to various transparent materials, such as polymers,ceramics or the like. Metals, which are available with a low cost and ahigh productivity, can be employed as an absorbing material.

The harmonic of the laser corresponds to visible light and provides thesame trend as above. The second harmonic permits producing a finerstructure and also employing inexpensive and high precision opticalelements in the focusing system.

Fourteenth Embodiment

By using an element produced with a process method according to one ofthe first to thirteenth embodiments, duplicates of the element areproduced. More specifically, a metal film is applied to the surface ofthe element and then an inverse forming die is formed therefrom by theelectroforming method. Thereafter, using the inverse forming die as aforming die, it is transferred to a polymer material by the formingmethod to form a duplicate thereof. The duplicate thus formed can againbe used as a forming die.

With such a procedure, either a profile corresponding to the processedstructure or the inverse profile can be produced for the other material.

In the method for processing a three-dimensional shape according to thefourteenth embodiment, a duplicate is formed with the aid of theelectroforming method with respect to the three-dimensional structureproduced by the process method of one of the above-mentionedembodiments. Moreover, using the duplicate of metal material, duplicatesof polymer or glass material are formed by the forming method. This isapplicable not only to the molding, but also to the forming die forphoto-curing resin used in the 2P method and to the forming die used inthe Sol-Gel method.

With this method, a three-dimensional structure can be obtained for amaterial different from the initially processed material. For instance,there is an advantage that, even if a material to be processed is nottransparent, the usage of a different material to form the forming diefor a transparent polymer permits producing transmission type elementswith duplication.

The laser process method requires a long time for a wide area to beprocessed, and has a drawback of increasing the cost. However, byproducing a metal mold and by producing duplicates for the mold,three-dimensional structures can be massively produced.

EXAMPLE 14

FIG. 15 shows steps of duplicating a structure in accordance with themethod of this embodiment.

As shown in FIG. 15(A), a step for applying a thin layer is firstlyexecuted to form a structure.

Subsequently, a three-dimensional structure is formed by a process laserlight, as shown in FIG. 15(B).

Subsequently, a metal layer 18 for producing a surface electrode in theelectroforming is formed by sputtering, as shown in FIG. 15(C).

Subsequently, a metal layer 19 of Ni is applied thereto by theelectroforming method, as shown in FIG. 15(D).

Subsequently, an original or master form f Ni is removed from thestructure thus processed, as shown in FIG. 15(E).

Subsequently, plastic material 20 is molded using the Ni master form asan original form, as shown in FIG. 15(F). Transparent structure can beproduced by polycarbonate material. Moreover, duplicates of photo-curingresin can also be produced by transfer method (2P method) using an UVlight.

By the above procedures, the structure having the same shape as that bythe laser process can be produced with low cost.

Fifteenth Embodiment

A method for producing a duplicate according to the embodiment 15 is thesame as that according to the embodiment 14, in which case, theduplicate is used as a stamper for videodisk. For this purpose, astructure including pits P and grooves for a videodisk in the form of adisk can be produced with the method according to one of the first tofourth embodiment to form a stamper for the videodisk by a method forsputtering Ni layer, electro-forming Ni layer and separating layer.

In the conventional method for preparing a stamper for videodisk, aphotosensitive material is applied onto a glass substrate by means of aspinner or the like and then baked. Thereafter, the substrate is exposedby a UV laser, such as He—Cd laser, and then a three-dimensional patternor the photosensitive material is produced after fixing and developing.Finally, a stamper is produced by applying a metal layer thereto withthe electroforming method and the separating process.

In this case, there are specific problems such as a difficulty indetermining the conditions for the exposure, fixation and development,the pollution due to the wash, and environment pollution due to thesolvent.

In the method for processing a structure according to this embodiment,the complicated processes can be simplified, because the structure canbe directly formed only by scanning the process laser light. In theconventional exposure method, a photosensitive material has to beilluminated by a UV laser having a high sensitivity for the material,whereas in the method according to the present invention, thetransparent layer and the thin layer for absorption of laser light canbe selected from a variety of materials without any special precautionabout the laser light source.

Since, moreover, the three-dimensional processing is carried out bymeans of one-shot laser light pulse, a high-speed process can beattained using light having a low energy.

EXAMPLE 15

FIG. 16 shows an example of a stamper for videodisk according to thepresent invention.

As shown in FIG. 16, a thin layer for absorption of laser light 2 isdeposited onto a flat substrate 1 of glass, and further a transparentlayer 3 is applied thereon. Then, a process laser light focused by anobjective lens having a large NA is irradiated during a short time ontothe surface of the transparent layer, in which case, a pit P is formedby one-shot pulse illumination. By rotating the substrate with arotation stage or by moving the substrate in the circumferentialdirection with a linear stage, the structure including pits arecontinuously formed. In this case, it is desirable that the totalthickness of the transparent layer 3 and the thin layer for absorptionof laser light 2 of metal material is determined by using a referencelight and it is preset to be ¼ of the wavelength of the reference light.

Furthermore, the process laser can be activated by adjusting the timingof radiation in synchronization with the movement of therotation/movement means, and the process laser light is irradiated afteradjusting the light intensity in accordance with the size of the hole.

In this case, a number of holes and/or a number of original forms can besimultaneously formed by splitting the laser light.

A duplicate can be produced from the original form produced by themethod according to this embodiment, and it can be used as a stamper byfurther duplicating the duplicate.

Sixteenth Embodiment

A duplication method of this embodiment is the same as that of thefourteenth embodiment. In this case, the duplicate is used as a masterfor diffraction type optical elements. A number of hole profiles isformed on a flat disk with the process method according to one of thefirst to fourth embodiments, and multi-level diffraction elements areformed in the form of a three-dimensional shape by shifting the processposition with movement means such as a stage or the like, or phasemodulation type diffraction grating is formed by processing the shapewith the aid of a computer.

In this case, the total thickness of the transparent layer and the thinlayer for absorption of laser light is set to be of order of λ/n where λis the wavelength of light irradiating the optical element.

Conventionally, a diffraction type optical element is formed in aprofile having a plurality of heights, for instance, by the combinationof resist pattern forming means and etching means in a multi-stage. Inthis process, a complicated and precise positioning of the masks isrequired, thereby causing increasing the process cost.

In the process method of this embodiment, the profile is directly formedonly by scanning the process laser light, thereby making it possible tosimplify the complicated steps in the conventional process.

In the conventional exposure method, it is necessary to use aphotosensitive material and to employ a UV laser, which is highlysensitive to the photosensitive material. In the method of thisembodiment, however, required materials can be selected from variousmaterials for the transparent layer and thin layer for absorption oflaser light.

Moreover, the process depth in a three-dimensional profile can bedetermined by the number of laser radiation events, and master or matrixfor diffraction elements, binary optical elements or the like can easilybe produced either by applying a metal layer to the processed materialor by applying the electroforming method thereto.

Seventeenth Embodiment

A laser process apparatus in this embodiment comprises a process laser;a ½-wavelength plate; laser light intensity regulating means such as apolarizing beam splitter or a ND (neutral density) filter; and laserlight forming means such as lenses and mirrors or the like, whereinlaser light radiation position is spatially determined and the laserprocess method according to one of the first to sixteenth embodiments isemployed.

In this case, it is desirable that means for controlling the number oflaser radiations, for instance, shutter is disposed inside or outsidethe laser process apparatus and that the laser light is irradiated insynchronization with a movement stage onto which a material to beprocessed is mounted.

The laser process apparatus permits processing a three-dimensionalstructure having a smooth bottom surface.

It is noted that such a structure can only be produced with difficultyby a process apparatus in the prior art.

Furthermore, a three-dimensional profile can easily be processed bycontrolling the laser radiation, and a large area process can be madeonly by moving the stage.

EXAMPLE 17

As shown in FIG. 17, a process laser light 32 emitted from a laserprocess apparatus 31 is introduced into a ½-wavelength plate 34 aftercontrolling the radiation time with an external shutter 33, wherein arotation of the ½-wavelength plate 34 causes the polarization plane ofthe process laser light 32 and the axial direction of the ½-wavelengthplate 34 to be changed, and then the beam intensity is controlled by apolarizing beam splitter 35. Thereafter, the process laser light 34,whose intensity is thus controlled, is reformed as for the beam shape byforming lenses 36 as the following lens system and by a mirror system37, and then transferred onto a mask 38. The process laser light 32passed through the mask 38 is focused by a condenser lens 39 and thenprojected in a reduced magnification onto the surface of a laminate 40as a material to be processed used for the layer application material.The laminate 40 as material to be processed is positioned in a processposition by a movement stage 41. In order to observe the laminate in theprocess position, an observation apparatus including an illuminationapparatus 42 is disposed and a state of the element can be monitored bya CCD camera 43.

With this system, a three-dimensional structure having a complicatedprofile can easily be processed.

As shown in FIG. 18, the process apparatus includes a laser device 31for emitting the process laser light 32; a pockels cell 31 a disposed inthe laser device 31; a galvanometer mirror 54 for scanning the processlaser light 32 emitted from the laser device 31; a fθ lens 56 forscanning the process laser light 32 reflected by the galvanometer mirror54 in a constant velocity; a movement stage 41 for mounting the laminate51 as a material to be processed according to one of the first toseventh embodiments; and a computer 53 for controlling the galvanometermirror 54 via the laser device 31, movement stage 41 and a galvanometercontroller 55.

As shown in FIG. 19, the computer 53 locates the laminate 51 as aprocess sample in a predetermined position at step S1. Subsequently, theprocess laser light 32 is emitted from the laser device 31 bycontrolling the pockels cell 31 a at step S2, and by scanning theprocess position with the galvanometer mirror 54 and fθ lens 56, aremoved material section is formed in the laminate 51 at step S3.

Subsequently, the laser radiation is ended at step S4 and then theformation of the profile is ended at step S5.

Eighteenth Embodiment

In this embodiment, a three-dimensional structure having partial flatsurfaces, which is formed by the laser process method according to oneof the above-mentioned embodiments, is used. Typically, the structurehas a process width of sub-micrometer to several hundreds micrometersand a process depth of several nm to several micrometers, and includes atransparent layer and a layer absorbing the process laser light.

Moreover, using a duplicate produced by the method according to one ofthe above-mentioned embodiments, a three-dimensional structure havingthe same shape as that of the duplicate can be produced from polymer,glass or the like.

The element produced by this method can be formed in a three-dimensionalstructure having a flat bottom surface, and, for instance, atransmission type optical element having a depth of order of a lightwavelength can be formed.

In conjunction with the above, a micro-sensor and a device formicro-machine can also be produced with the three-dimensional processingaccording to this embodiment.

In accordance with this embodiment, components can be produced neitherby using complicated processes nor by vacuum process, so that large-sizecomponents, such as large-sized optical elements, devices having a largearea can easily be produced.

Nineteenth Embodiment

By using a three-dimensional structure having a partial flat surface orits duplicate with the laser process method according to one of theabove-mentioned embodiments, a component having a reflection layer of Alor the like on at least one surface can be formed by evaporation,sputtering or the like.

The structure has typically a process width of sub-micron to severalhundred micrometers and a process depth of several nm to severalmicrometers as well as at least one reflection layer.

A three-dimensional structure having a flat bottom surface can beprovided to a component produced by the method according to thisembodiment, and, for instance, a reflection type optical element havinga depth of order of a light wavelength can be produced.

In the prior method, complicated process steps are required to form areflection type optical element. However, in the method according to thepresent embodiment, a reflection type optical element is formed in ahigh precision and in a reduced cost by directly processing athree-dimensional structure with a laser light and by applying areflection layer thereto in the final stage.

While preferred embodiments have been shown and described, variousmodification and substitutions may be made without departing from thespirit and scope of the invention. Accordingly, it is to be understoodthat the present invention has been described by way of example, and notby limitation.

[Advantages Resulting from the Invention]

As described above, the following advantages can be obtained by thepresent invention.

In accordance with the invention defined by the first aspect, a methodfor processing a three-dimensional structure can be provided, whereinthe structure has a fine three-dimensional shape and a flat surface, sothat it is usable for an optical device.

In accordance with the invention defined by the second aspect, the thinlayer for absorption of laser light has a larger thermal diffusion ratethan the flat substrate, and therefore the thin layer for absorption oflaser light can be easily separated from the flat substrate.

In accordance with the invention defined by the third aspect, the totalthickness of the transparent layer and the thin layer for absorption oflaser light removed corresponds to the one-shot pulse radiation, andtherefore the process can be carried out at a greater rate, and thedepth control can be carried out at a higher precision, compared withthose in the conventional laser abrasion method.

In accordance with the invention defined by the fourth aspect, a thermalinsulation layer is interposed between the flat substrate and the thinlayer for absorption of laser light, the selectable range of thematerial usable for the flat substrate expands. For instance, a layerhaving a less flatness can be used as the flat substrate.

In accordance with the invention defined by the fifth aspect, theprocess depth can be controlled by the number of pulses in the laserlight radiation, so that an optical element, such as a multi-binarydiffraction optical element, a hologram optical element or the like caneasily be produced.

In accordance with the invention defined by the sixth aspect, thethermal diffusion area can be reduced.

In accordance with the invention defined by the seventh aspect, therange controllable for the process depth can be expanded withoutaltering the intensity of the laser light radiation by controlling thethickness of the transparent layer in the initial stage. As a result,the material depth varying in a spatial position can be digitallycontrolled only by the number of pulses in the laser radiation, and forinstance, a phase modulation element or the like can bespatial-selectively formed on a single substrate.

In accordance with the invention defined by the eighth aspect, a processpattern corresponding to a mask pattern can be formed either byprojecting a mask pattern in a reduced magnification of imaging or byexposing in a contact with a mask.

In accordance with the invention defined by the ninth aspect, athree-dimensional structure having a varied shape can be formed bychanging the radiation position of the process laser light.

In accordance with the invention defined by the tenth aspect, a removedmaterial section having a round bore shape can be formed.

In accordance with the invention defined by the eleventh aspect, aremoved material section in the form of a straight line can be formed,so that a diffraction type optical element, a multi-level diffractionelement or the like can be produced.

In accordance with the invention defined by the twelfth aspect, athree-dimensional shape product having a material different from theprocess material can be produced.

In accordance with the invention defined by the thirteenth aspect, aprofile is directly formed by using the laser light, and therefore lightmemory mediums can be produced in a simple process, compared with thatin the prior art.

In accordance with the invention defined by the fourteenth aspect, aprofile is directly formed, using the laser light, and thereforediffraction optical elements can be produced in a simpler process,compared with that in the prior art.

In accordance with the invention defined by the fifteenth aspect, anapparatus for processing a three-dimensional structure having a finethree-dimensional profile and a flat surface can be provided, where thethree-dimensional structure is used as an optical device.

In accordance with the invention defined by the sixteenth aspect,three-dimensional structures having a varied shape can be produced.

In accordance with the invention defined by the seventeenth aspect,three-dimensional structures having a complicated profile can beproduced and a wide area process is feasible.

In accordance with the invention defined by the eighteenth aspect,three-dimensional structures having a complicated profile can beproduced and a wide area process is feasible.

In accordance with the invention defined by the nineteenth aspect, thethermal diffusion area can be reduced.

In accordance with the invention defined by the twentieth aspect, theprocess depth can be digitally controlled by the number of laser lightradiation pulses, and therefore an optical element, such as amulti-binary diffraction optical element, a hologram optical element orthe like, can be produced.

In accordance with the invention defined by the twenty-first aspect, athree-dimensional structure having a fine three-dimensional profile anda flat surface can be obtained, where the three-dimensional structure isused as an optical device.

In accordance with the invention defined by the twenty-second aspect,the thin layer for absorption of laser light has a larger thermaldiffusion rate at a depth of a laser light being incident just thereonthan at a greater depth, so that the removal of the thin layer forabsorption of laser light from the interface is promoted.

In accordance with the invention defined by the twenty-third aspect, thethin layer for absorption of laser light has a higher thermal diffusionrate than the flat substrate and therefore the separation of the thinlayer for absorption of laser light from the flat substrate is promoted.

In accordance with the invention defined by the twenty-fourth aspect, athermal isolation layer is interposed between the flat substrate and thethin layer for absorption of laser light, so that a selectable range ofmaterial suitable for the flat substrate expands. For example, amaterial having unevenness can be used as a material for the flatsubstrate.

In accordance with the invention defined by the twenty-fifth aspect, anoptical element, such as a multi-binary diffraction optical element, ahologram optical element or the like can be obtained.

In accordance with the invention defined by the twenty-sixth aspect, athree-dimensional structure such as a phase modulation element, whoseproperty varies in accordance with the depth, can be obtained.

In accordance with the invention defined by the twenty-seventh aspect, ametal can easily be applied to a material in the form of a thin film,and advantageously provides a very small production cost.

In accordance with the invention defined by the twenty-eighth aspect, apolymer is used as the material for a transparent layer, so that thetransparent layer having a well-controlled layer thickness can beproduced with a reduced cost.

In accordance with the invention defined by the twenty-ninth aspect, theprocess depth can be controlled in a high precision, along with anincrease in the amount of removal, so that a high quality process isfeasible.

In accordance with the invention defined by the thirtieth aspect, athree-dimensional structure having a various profile can be obtained.

In accordance with the invention defined by the thirty-first aspect, theshaping of the structure is directly carried out by the laser light,thereby enabling a reflection type optical element to be produced insimplified steps, compared with the complicated steps in the prior art.

1. A three-dimensional structure comprising: a flat substrate having aflat surface; a thin layer for absorption of laser light laminated onsaid flat substrate; and a transparent layer laminated on said thinlayer, wherein a thickness of each of the thin layer and the transparentlayer is adjusted so that when process laser light is irradiated on thetransparent layer at a laser-irradiated area, the process laser light isabsorbed in the thin layer after passing through the transparent layer,and the transparent layer and the thin layer are removed by an energy ofthe absorbed laser light over all of the laser-irradiated area where theprocess laser light is irradiated, to expose the flat surface of theflat substrate over all of the laser-irradiated area, and said thinlayer for absorption of laser light and said transparent layer arefurther alternately laminated in a plurality of pairs, and each removedmaterial section has a depth different from each other.
 2. Athree-dimensional structure as claimed in claim 1, wherein thethicknesses of said transparent layers are different from each other. 3.A three-dimensional structure comprising: a flat substrate having a flatsurface; a thin layer for absorption of laser light laminated on saidflat substrate; and a transparent layer laminated on said thin layer,wherein a thickness of each of the thin layer and the transparent layeris adjusted so that when process laser light is irradiated on thetransparent layer at a laser-irradiated area, the process laser light isabsorbed in the thin layer after passing through the transparent layer,and the transparent layer and the thin layer are removed by an energy ofthe absorbed laser light at the laser-irradiated area where the processlaser light is irradiated, to expose the flat surface of the flatsubstrate of the laser-irradiated area, and said thin layer forabsorption of laser light and said transparent layer are furtheralternately laminated in a plurality of pairs, and each removed materialsection has a depth different from each other.
 4. A three-dimensionalstructure as claimed in claim 3, wherein the thicknesses of saidtransparent layers are different from each other.